High Brightness Electron Beam Diagnostics and their ... - CASA

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shortterm,touseasbeamdensitymonitorintheFELdriver,aluminumfoilsinthepopularcon- ExperimentalSetup Althoughthecarbonfoilmonitorisveryusefulasanoninterceptivedevice,wedecided,forthe 4.3.2ProleMonitorCongurationintheFEL serted/withdrawnfromthebeampathbythemeansofanaircylinderactuator.Inthiscongurationthebackwardtransitionradiationemittedat90degwithrespecttothebeamaxisshinesout ofthevacuumchamberthroughasilicaopticalwindow.Itisthencollectedbyaplanarmirrorand diameterthatmakesa45deganglew.r.t.thebeamdirection.Thefoilcanberemotelyin- diagnosethebeamqualityinacontinuousandnonintrusivefashion. Thesystemweuseconsistsof0:8mthickaluminumfoilsmountedonacircularframesof19mm verythincarbonfoilonlargesupport.AlsointhecaseoftheFEL,thelaseritselfcanserveto gurationaspicturedingure4.11.Thischoiceisinpartduetothedicultytoreliablymount thehighestpossibleresolutionwithareasonableeldofview.Thecircularframeonwhichthefoil ismounteddeterminestheeldofview:this19mmdiameterframeisusedtoaccuratelycalibrate theimageandtherebydeterminewhatistheconversionfactorbetweentheCCDarraypixelsand triggered.ThesystemissettoimagethefoilplaneontheCCDarraydetectorwithmagnication ofapproximately1=3.Thechoiceofthemagnicationratioisdictatedbytheneedofachieving senttoanopticalsystemcomposedofacommerciallyavailabletelephotolens(optimizedtoreduce chromaticandsphericalopticalaberration)andahighresolutionCCDcamerawhosevideooutput signalisdigitizedbyaVME-basedDATACUBEimageprocessingboardthatcanbeexternally realdistancesinthefoilplane. Toavoiddamagingthealuminumfoil,andsincethebeamdynamicsisonlydominatedbysinperbunch,thebunchrepetitionrateinamacropulse,themacropulsewidthandthemacropulse repetitionrate.Sinceonlythechargeperbunchaectsthephasespaceandconsequentlythebeam Therearefourindependentparametersthatcaninuencethebeamaveragecurrent:thecharge Figure4.11:StandardcongurationoftheOTR-basedprolemonitorintheFEL-driveraccelerator. glebuncheect,i.e.thebeamphasespacedensityonlydependsonthechargeperbunchand notonthebunchrepetitionrate,thebeamaveragecurrentisdecreasedtoapproximately0:5A. Incident Beam OTR Radiator Beam Sync Mirror Telephoto Lens Charge Coupled Device Camera VIDEO IN EXT TRIGG To EPICS control system
densityprole,byactingontheotherthreeparametersitispossibletoreducethebeamcurrent withoutaectingonthephasespacedistribution.Naturallythefactwehavetouseareduced beamcurrentduringthemeasurementofthebeamparameterimpactsontheFELoperationand subsequentexperiments.Thereforesuchameasurementisinvasive.AswehaveseeninChapter2, Intensity (a.u) 2 7 6 5 8 109 4 4 3 2 -6 -3 0 3 6 . .. ..... ... . ........ .. .. . ... . .. . .. . .... ....................................................................................... .. .. ....... .. .... .... .. .... .. .. . . . .. .. . .. .. . .. ... .. . ... .. . . .. . .. . .. . . . .. .. ... .... .... . . . 10 5 2 -6 -3 0 3 6 Distance (mm) 12 10 5 22 10 5 32 10 5 42 Figure4.12:Rawdatabeamprole(topgraph)andbeamproleafterprocessing(background whichalsosynchronouslygeneratea5Vrectangularpulsewhosewidthandrepetitionratearethe replicaofthemacropulse.Suchsignalcalledthe\beamsync"isavailablefromthecontrolsystem totriggerdataacquisitionsystems. Inthepresentcase,wetriggertheimageprocessingboardtograbonlythevideoframethatcon- atarepetitionrateupto74:85MHz.Allthebeamstructureisgeneratedbyamasteroscillator subtracted,ghostpulsecontributionremoved,...). tainsthebeamimage.Forsuchapurposeweusethefollowingsetup:the\beamsync"isdelayed by0:435msbeforebeingsenttothe\externaltrigger"inputoftheimageprocessingboard.The eachmacropulsecontainsbunches(whosechargecanbearbitraryvariedfrom0pCto135pC6) SomeprimaryoperationsonthisdatastreamcanbedirectlyperformedbytheCPUoftheimage processingboardinrealtime[39].Suchoperationsincludethecalculationof: delayissetsothatthedigitizeristriggeredatthenextincomingpulse. Thedigitizeddatastreamattheimageboardoutputconsistsofa660484arraymatrix,I(x;y). 6Intheresultspresentedinthisreportthemaximumchargeusedisapproximately60pC Intensity (a.u)
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HighBrightnessElectronBeamDiagnosti
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eratedupto48MeVpriortothelasingsyst
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IthanktheCEBAFmachineoperators,with
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3.4MeasurementoftheLongitudinalResp
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5.6ZerophasingTechniqueforBunchLeng
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ListofTables 3.2Comparisonofcoecien
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ListofFigures 1.1Comparisonoftheexp
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3.11Momentumcompactionandnonlinearm
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4.18Overviewofthephasespacesampling
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5.16Interferogrammeasuredfordierent
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6.10Comparisonofthermstransversehor
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Chapter1 UVdomainandareplannedtogen
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space-chargeinthelowenergyregime,an
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!Vjitsthevelocity,and!Xjisthepositi
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equation boundarybetweenvacuumandam
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10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.
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1.0 0.8 0.6 0.4 0.2 E=10 MeV E=42 M
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00000000000000000000000000000000000
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Page 39 and 40: Bu(rms)0.28T ParameterValueUnit Nu
Page 41: 2.7TheJeersonLabIRproject usedasexp
Page 44 and 45: Study TheFELdriveraccelerator:Latti
Page 46 and 47: ParameterValue x -0.178 x(m) 8.331
Page 48 and 49: Thepurposeofmeasuringthetransverser
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Page 60 and 61: Experimentallythecalibrationcoecien
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Page 70 and 71: 10 5 Sext. ON Figure3.20:Eectofthes
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Page 86 and 87: Actuator Inserts Foil and Mirror CI
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Page 94 and 95: Let'sassumethethinlensapproximation
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Page 121 and 122: Population Population 100000 90000
Page 123 and 124: Theequation5.8yields: f()=jZ+1 11Xn
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expansionoftheBFFderivedinthischapt
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Asarstapproximation,wecanestimatetr
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errorpropagation8theoryappliedonEqn
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inducedbyspacechargeisnotaconcernin
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Golay Cell Signal (V) Golay Cell Si
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Golay Cell Ouput (V) Golay Cell Oup
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150 100 5 4 Figure5.19:Energyspectr
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Figure5.23:picturaleectoflongitudin
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. .. .. . .. . . .. . .. . . .. . .
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σ x (m) x 10−3 5 4 3 2 1 0 0 5 1
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BeamDynamicsStudies Chapter6 undula
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x,y (mm) 6.0 4.8 3.6 2.4 1.2 x y 0.
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Space Charge over Emittance Ratio (
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numericalsolution[56].Thisapproxima
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0.03 . .... . .. ... . .. ..... . .
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ε x (mm−mrad) Nominal 6 4 2 cryo
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2.2 2 1.8 Figure6.10:Comparisonofth
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6 4 2 Figure6.12:\R55"transfermapfo
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10 1 5 10 0 500 1000 1500 2000 2500
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EnergySpread(%) BunchLength(mm) Par
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15 Effect of RMS energy Spread 10 F
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6.4.4BunchSelfInteractionviaCoheren
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100 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0
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Inthesecondseriesofrun,wewereableto
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Conclusion Chapter7 Therecirculator
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[2]Y.Shibata,T.Takahashi,T.Kanai,K.
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[29]J.-C.Denard,C.Bochetta,G.Traomb
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[65]B.C.Yunn,\ImpedancesintheIRFEL"
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TEM:transverseelectricmagnetic. TOF
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B.2Anoteonspacecharge Wedenetheslop
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B.3.3PARMELA FeaturesofJeersonLabVe
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Initialization MAIN Stop INPUT DECK
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C.0.6TheDispersionRelationsfor^S(!)
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have: Howeveritshouldbenotedthatweh
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FigureD.1:OverviewoftheRF-controlsy
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High Brightness Electron Beam Diagnostics and their ... - CASA

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